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Author Topic: Spark when the key is turned off  (Read 1066 times)

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Offline DJT96

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Spark when the key is turned off
« on: July 30, 2007, 05:57:29 PM »
For some unknown reason the plugs fire when I turn either the key switch or the kill switch off(bike not running or turning engine over).  Any idea why?  I have a 71 cb750 k1 with dyna 3.0 ohm coils and Dyna s ignition. I also have a new main wiring harness.


Thanks  DJ
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Offline 333

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Re: Spark when the key is turned off
« Reply #1 on: July 30, 2007, 06:17:41 PM »
Are we talking a single spark, or will it continue to run?
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Offline OldSchool_IsCool

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Re: Spark when the key is turned off
« Reply #2 on: July 30, 2007, 06:35:00 PM »
Sounds like the key and kill switch have somehow been bypassed.  Like the coils are hooked up to unswitched 12v.  How do you stop the engine?  Turn off the gas?
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Offline DJT96

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Re: Spark when the key is turned off
« Reply #3 on: July 30, 2007, 08:11:17 PM »
The kill switch and key will turn the bike off while running. Without the engine running if you turn the key on and then off the plugs will spark.
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Offline batdan

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Re: Spark when the key is turned off
« Reply #4 on: July 30, 2007, 08:24:12 PM »
I think that would be normal as by turning the key on the coil is getting power and then when you turn it off the power is interrupted which causes a spark. This is basically the same thing the points do.

Also apparently if you leave the ignition on but don't run the bike it'll kill your battery....
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Offline Steve F

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Re: Spark when the key is turned off
« Reply #5 on: July 30, 2007, 10:12:06 PM »
Quote from: batdan on July 30, 2007, 08:24:12 PM
I think that would be normal as by turning the key on the coil is getting power and then when you turn it off the power is interrupted which causes a spark. This is basically the same thing the points do.

Also apparently if you leave the ignition on but don't run the bike it'll kill your battery....
I agree.....that's exactly what's happening.  I also means that the coil sending the spark is energized with the key on, and the points are conducting (or shorted to ground).  Break the circuit, either by opening the points or simply turning off the key will produce a spark.
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Dodgy CB550f1

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Re: Spark when the key is turned off
« Reply #6 on: July 31, 2007, 05:19:46 AM »
Its because of the dyna electronic ignition they all do it, I dont know why but they do, I know this because I was checking for a spark at the plugs on my Z1 and was holding ht lead in my hand when I turned the ignition on  :o  :D
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Offline eurban

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Re: Spark when the key is turned off
« Reply #7 on: July 31, 2007, 05:58:24 AM »
Yes my k8 with a Dyna III does this . . .
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Offline DJT96

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Re: Spark when the key is turned off
« Reply #8 on: July 31, 2007, 03:04:52 PM »

Thats how I found out  ;D

Thanks for the replies

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Quote from: Dodgy CB550f1 on July 31, 2007, 05:19:46 AM
Its because of the dyna electronic ignition they all do it, I dont know why but they do, I know this because I was checking for a spark at the plugs on my Z1 and was holding ht lead in my hand when I turned the ignition on  :o  :D

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